1 #define SIRENE_PORT PORTB
2 #define SIRENE_DDR DDRB
3 #define SIRENE_PIN 4
4
5 void setup() {
6 init_tone2();
7 }
8
9 volatile uint32_t ever = 0;
10
11 void loop() {
12
13 delay(2000);
14 for (int i = 0; i < 2; i++)
15 {
16 tone2(262, 200);
17 delay(200);
18 tone2(330, 200);
19 delay(200);
20
21 tone2(262, 200);
22 delay(200);
23 tone2(330, 200);
24 delay(200);
25
26 tone2(392, 400);
27 delay(400);
28
29 tone2(392, 400);
30 delay(400);
31 }
32 }
33
34 void init_tone2()
35 {
36 TCCR2A = 2;
37 TCCR2B = 0;
38 TIMSK2 = 2;
39 SIRENE_DDR |= (1 << SIRENE_PIN);
40 }
41
42 static volatile uint8_t tone2_state;
43 static volatile uint32_t tone2_len;
44
45 ISR(TIMER2_COMPA_vect)
46 {
47 ever++;
48 if (tone2_state)
49 {
50 SIRENE_PORT |= (1 << SIRENE_PIN);
51 tone2_state = 0;
52 }
53 else
54 {
55 SIRENE_PORT &= ~(1 << SIRENE_PIN);
56 tone2_state = 1;
57 }
58 if ((--tone2_len) == 0) TCCR2B = 0;
59 }
60
61 void tone2(uint16_t freq, uint16_t duration)
62 {
63 uint32_t period = 1000000 / freq;
64
65 if (freq >= 977) // prescaler 32
66 {
67 tone2_state = 0;
68 tone2_len = ((uint32_t)duration * (uint32_t)1000) * 2 / period;
69 TCNT2 = 0;
70 OCR2A = (uint8_t) (250000 / (uint32_t)freq);
71 TCCR2B = 3;
72 }
73 else if (freq >= 488) // prescaler 64
74 {
75 tone2_state = 0;
76 tone2_len = ((uint32_t)duration * (uint32_t)1000) * 2 / period;
77 TCNT2 = 0;
78 OCR2A = (uint8_t) (125000 / (uint32_t)freq);
79 TCCR2B = 4;
80 }
81 else if (freq >= 244) // prescaler 128
82 {
83 tone2_state = 0;
84 tone2_len = ((uint32_t)duration * (uint32_t)1000) * 2 / period;
85 TCNT2 = 0;
86 OCR2A = (uint8_t) (62500 / (uint32_t)freq);
87 TCCR2B = 5;
88 }
89 else if (freq >= 122) //prescaler 256
90 {
91 tone2_state = 0;
92 tone2_len = ((uint32_t)duration * (uint32_t)1000) * 2 / period;
93 TCNT2 = 0;
94 OCR2A = (uint8_t) (31250 / (uint32_t)freq);
95 TCCR2B = 6;
96 }
97 else if (freq >= 30) //prescaler 1024
98 {
99 tone2_state = 0;
100 tone2_len = ((uint32_t)duration * (uint32_t)1000) * 2 / period;
101 TCNT2 = 0;
102 OCR2A = (uint8_t) (7813 / (uint32_t)freq);
103 TCCR2B = 7;
104 }
105 }
